Vesicular Basalt

Physical Properties

Mohs hardness 5-6; Color: Grey to dark black with white/light beige weathering; Luster: Dull or sub-metallic; Crystal structure: Aphanitic (fine-grained) with visible vesicles (gas bubbles); Specific gravity 2.8-3.0.

Formation & Geological History

Formed from the rapid cooling of magnesium-rich and iron-rich lava at or very near the Earth's surface. The small holes (vesicles) are created by gas bubbles that were trapped in the lava as it solidified.

Uses & Applications

Used in construction as road base, concrete aggregate, and railroad ballast. Highly vesicular varieties (scoria) are used in landscaping and as abrasive cleaners (pumice stone).

Geological Facts

Basalt is the most common rock type in the Earth's crust and makes up most of the ocean floor. It is also found extensively on the Moon and Mars.

Field Identification & Locations

Identify by its dark color, heavy weight (relative to size), and the presence of small holes or pits. It is commonly found in volcanic fields, oceanic islands, and mid-ocean ridges.

Identified on: 4/30/2026

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